This will keep a few weeks in the refrigerator or months in the freezer. Add a tablespoon to scrambled eggs or sauces for a wonderfully concentrated mushroom taste. This is a great addition to a quick pan sauce. I was originally inspired by a Paula Peck recipe and have evolved this recipe over the years. How I use thinly sliced mushrooms in order to retain some mushroom texture and appearance. I also make a similar 'preserve' with coarsely diced onions when I buy a large bag of onions..

I usually use butter these days and let it brown before adding other ingredients. If you feel brave you can start melting/browning the butter while slicing and dicing the mushrooms but it would be safer to wait until all the ingredients are ready to cook.

Put the butter or oil, salt and cayenne (and optional onions/garlic/shallots) in a wide heavy skillet (or Dutch Oven) with a lid. Heat and cook any onions to a translucent state. Add the mushrooms and cover.

Continue to heat to medium.After a few minutes the mushrooms will give off a lot of liquid. Stir well to coat the mushroom and replace the lid, leaving it slightly ajar if it is very tight-fitting. Leaving the pan covered, continue to cook for about 30 minutes, or until the liquid mostly dries up.Remove the cover and set aside.Cook gently for another 10 minutes or until dry.Store tightly covered in the refrigerator or freezer.